JPH0611918B2 - Surface-treated steel plate for cans - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention forms a surface-treated steel sheet for cans, particularly a steel sheet punched into a circular shape into a cup shape by drawing, or further, A two-piece can (a squeeze can or a D can that is manufactured by thinly molding the side wall of a molded cup-shaped product by ironing (lroning).
The present invention relates to a surface-treated steel sheet for drawn and ironed cans.

[Prior Art and Its Problems] Food cans are made of tin-plated steel sheets, chrome-plated steel sheets, aluminum sheets, or the like.
There are two-piece cans and two-piece cans. The 3-piece can has a lid,
The body and bottom are formed separately, and these are joined by soldering, welding, winding, etc. On the other hand, in the two-piece can, the body and the bottom are integrally formed, and the lid is joined thereto. That is, a two-piece can is formed by drawing a metal plate punched out in a circular shape in the first step of processing into a cup shape by drawing (drawing), or by further passing a cup-shaped molded product thus formed through a die. The outer die and the inner punch are ironed to reduce the thickness of the side wall of the body while increasing the length of the body (lroning).

In particular, the two-piece can manufactured by DI molding has the advantages that it is thinner and lighter than the three-piece can, and it has no seams and no leaks. Therefore, its demand is great, and its application in the future. Is also expected to expand.

At present, surface-treated steel sheets such as tin-plated steel sheets and aluminum materials are used as the materials for DI cans, but in particular, surface-treated steel sheets are cheaper than aluminum materials, and thus demand for them is expected to grow. However, as described above, two-piece cans, especially DI cans, require extremely rigorous processing when integrally forming the bottom of the body, and severe conditions are imposed particularly on the plating film of the surface-treated steel sheet. . For this reason, in the case of tin-plated steel sheets and chrome-plated steel sheets that have been conventionally used as materials for cans, deterioration of the plating film cannot be avoided by DI molding. For example, in the case of a tin-plated steel sheet, Sn on the steel sheet plays a role of a lubricant during ironing as well as securing corrosion resistance.
It is suitable as a plating material for the outer surface of a can steel sheet. However, tin-plated steel sheets have the following drawbacks. As a result of the tin plating film on the inner surface of the can directly contacting the forming tool during ironing, cracks occur in the tin plating film and the steel material is exposed. When the steel material is exposed in this way, the secondary corrosion resistance (undercutting corrosion) of the inner surface of the can after coating deteriorates, and Fe elutes in the filling material such as the beverage filled in the can and the life of the can And the taste and aroma (flavor) of the contents are impaired. Therefore, conventionally, after DI molding, a sealing treatment for covering the exposed steel ground surface has been performed with a phosphoric acid treatment liquid or a chromium phosphate treatment liquid. Even if such a treatment is performed, the corrosion resistance on the inner surface side is not always sufficient.
It has been attempted to secure the corrosion resistance by coating the organic coating more than once, but these have led to an increase in cost.

Further, since the ring portion of the can bottom on the outer surface of the can after DI molding is often used unpainted, there is a drawback that it easily rusts during storage or transportation.

On the other hand, TFS (chromium plated steel sheet) has a film of chromium hydrated oxide on the chromium plated layer electrodeposited from an aqueous solution, but the chromium plated layer is hard and is similar to Sn plated steel sheet. A film defect is caused by DI molding on the. To compensate for this, apply thermosetting paint on both sides,
Attempts have also been made with the intention of compensating for the lubrication effect and the deterioration of the corrosion resistance under the coating film (for example, JP-A-55-8279).
No. 7), the corrosion resistance under the coating film is not sufficient, and the can body adheres to the punch due to the coating film during the ironing, and it takes more than the strength of the can body to pull out the punch, and the warp occurs at the mouth of the can body. Chromium-plated steel sheets have not been put into practical use because they have drawbacks such as so-called rollback.

Further, when the DI formability and the corrosion resistance of the steel sheet which was subjected to Al plating (including multiple layers) to improve the corrosion resistance were examined, it was found that mold galling occurred during DI forming and the appearance was significantly deteriorated.

[Problems to be Solved by the Invention] As described above, in the conventional surface-treated steel sheet, a sealing treatment is required after DI forming like a tin-plated steel sheet, or a coating treatment is performed like a chrome-plated steel sheet. However, the corrosion resistance under the coating film is insufficient, and an excessive force is required to pull out the punch, which causes rollback or shortens the life of the die due to galling during molding.

In order to solve such a problem, the present invention has been made, and a two-piece can, which maintains the weather resistance and the under-coating corrosion resistance on the outer surface side even when DI molding is performed and has excellent DI moldability, It is to provide a surface-treated steel sheet for a DI can.

[Means and Actions for Solving the Problems] The surface-treated steel sheet for a two-piece can of the present invention has a thickness of 0.05 to 5.0 μm of Al-S on the surface of the steel sheet that is at least the outer surface of the can.
An n-alloy coating is provided, and a steel sheet having a thickness of 0.01 to 1.
0 μm Cr film, Al-with a thickness of 0.05-5.0 μm on top of it
It is characterized by providing a Sn alloy film (Al-Sn / Cr2 layer).

In order to obtain sufficient lubricity, Sn in the Al-Sn alloy should be
The content must be 1 wt% or more, preferably 5-
60 wt% is good.

Hereinafter, the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1A, an Al—Sn alloy coating 2 is provided on at least one surface of the cold rolled steel sheet 1 in order to secure DI formability. Since the Al-Sn alloy is a eutectic reaction type, it does not form a solid solution in the solid state. In particular, in the case of Al-Sn alloy plated material produced by vacuum deposition or melting method, Al
Phase and Al-Sn eutectic phase exist, and Sn contained in the film during DI molding is heated by friction heat and oozes out to serve as a lubricant. As a result, excellent lubricity is exhibited, and normal DI molding is possible. In order to obtain sufficient lubricity for DI molding, Sn content of 1 wt% or more is required. If the Sn content exceeds 60 wt%, the weather resistance and the appearance after molding deteriorate, and in addition, Sn is expensive and is not economical. Therefore, judging from the lubricity, corrosion resistance and appearance, the Sn content is preferably 5 to 60 wt%. Further, in order to obtain sufficient lubricity, a film thickness of 0.05 μm or more is required, but exceeding 5 μm is not economical. Therefore, in the present invention, the film thickness of the Al—Sn film is set to 0.05 to 5.0 μm.

If corrosion is significant due to the contents and storage environment, Al-
It is preferable to provide the Cr film 3 under the Sn film 2 in the range of 0.01 to 1.0 μm (see FIG. 1B). The Cr film evenly covers and protects the base steel and has a large polarization resistance.
The sacrificial dissolution of the 1-Sn film can be suppressed, and the can life can be extended. In order to obtain a sufficient protective effect, a film thickness of 0.01 μm or more is necessary, but since it is not economical to exceed 1.0 μm, the film thickness range of 0.01-1.0 μm is set in the present invention.

[Examples] Examples according to the present invention will be described below.

Example 1 A vacuum vapor deposition apparatus equipped with two water-cooled copper crucibles was used to obtain a plate thickness of 0.
Al-Sn co-deposited plating material (Sn content: 5 to 48%, film thickness 0.5 to 4.3) on both surfaces of a 3 mm low carbon aluminum killed steel plate.
6 kinds (No. 1 to No. 6), and after plating Cr (0.03 to 0.75 μm) on the lower layer by ion plating,
Al-Sn co-deposition plated material (Sn content: 11 to 11
54 wt%, film thickness 0.6 to 3.7 μm, 4 types (No. 7 to No. 1)
0) Prepared. The cross-section of the coating composition is shown in FIG. 1A.

Example 2 After degreasing and pickling a low carbon aluminum killed steel sheet, Al and S
It was immersed in a molten metal in which n was mixed and melted, and four types of Al-Sn alloy plated steel sheets (No. 11 to No. 14) were produced. The film thickness is 0.
The content was 6 to 4.1 μm and the Sn content was 5.1 to 58%. The cross-section of the coating composition is shown in FIG. 1A.

Comparative material Sn coating, Cr by electroplating on the steel sheet surface of the example
+ Cr _OX coated 3 types of plated steel sheets (No.15 to N
o.17) was prepared.

The plated steel sheet thus obtained was subjected to the following tests to evaluate DI formability and corrosion resistance. DI
For the molding, the co-test material was punched into a disk with a diameter of 123 mm, this was molded into a cup with an inner diameter of 72 mm and a height of 36 mm with a commercially available cupping press, then this cup was inserted into a DI machine and the coolant at 40 ° C was circulated. Using the punch speed of 30 m / min and the stroke of 600 mm, the redrawing process and the three-stage ironing process were performed. The formed can body has an inner diameter of 52 mm and a height of 130 mm, and the thickness of the can body is about half the original thickness.

The moldability was calculated by calculating the energy required for molding from the molding load and the amount of deformation, and evaluated by the calculated value. The smaller the molding energy, the better the moldability. The stripping property was evaluated by the force required to pull out the punch from the molded can body. The smaller the force, the better the stripping property.

Regarding the corrosion resistance, an HCT (wet) test is conducted for the purpose of investigating the weather resistance, and a UCC test is conducted for the purpose of investigating the corrosion resistance under the coating film.
A PV test was conducted and evaluated.

The HCT test was performed by degreasing and cleaning the molded can body, sealing the back surface and the end surface, and observing the rusting condition in a humid environment at a temperature of 50 ° C. and a temperature of 80%.

In the UCC test, the molded can body is degreased and washed, and a paint for a can (on the outer surface side, a vinyl-modified alkyd resin of about 50 μm is used).
It is baked and painted with a thickness of m.
Copolymer coating of vinyl acetate and maleic acid is applied to a thickness of about 50 μm. ) Was applied. Then, the test piece was cut into a size of 50 mm × 70 mm, a cross cut reaching the base material was cut into the coating film, and the back surface and the edge portion which were not to be tested were sealed. After immersing this in a corrosive liquid for 96 hours, a tarp was attached to the coating film, and this was peeled off, and the corrosion width and the peeled state of the coating film at this time were observed. The corrosive liquid is
An aqueous solution containing citric acid 1.5% and sodium chloride 1.5% at 35 ° C.

The IPV test measures the amount of iron dissolved from the can material in the contents of the can.
After storing at 8 ° C. for 6 months, the eluted Fe ions were quantitatively determined.

As can be seen from Table 1, in the examples, the molding energy is small and the stripping property is good. Since it is molded smoothly, the plating film does not deteriorate and the inner and outer surfaces have good corrosion resistance. Especially, the lower layer is made of Cr by ion plating.
The plated products (No. 7 to No. 10) showed excellent corrosion resistance. On the other hand, tin-plated steel sheet (No.15)
Was excellent in DI moldability, but was poor in corrosion resistance. Cr
The galvanized steel sheets (Nos. 16 and 17) had galling between them and the die when there was no lubricating coating film, and the forming energy increased. Comparing the comparative example showing the prior art with the embodiment of the present invention, it can be seen that the embodiment exceeds the prior art in all test items.

[Effects of the Invention] As described above, the surface-treated steel sheet according to the present invention is
The Al-Sn alloy has excellent corrosion resistance, and since Sn contained in the film acts as a lubricant, it has moldability equal to or higher than that of conventional tinplate, particularly DI formability and corrosion resistance that exceeds tinplate. . Further, since it is not necessary to treat with phosphate after molding, the can manufacturing cost is lowered in combination with the stable molding operation. As described above, the effect of the present invention is great and contributes to the can manufacturing technology.

[Brief description of drawings]

1A and 1B are schematic cross-sectional views showing an example of the surface-treated steel sheet for cans of the present invention. 1 ... Steel plate, 2 ... Al-Sn alloy film, 3 ... Cr film.

Claims (2)

[Claims] 1. A surface-treated steel sheet for cans, wherein an Al—Sn alloy coating having a film thickness of 0.05 to 5.0 μm is provided on at least the outer surface of the steel sheet for cans. 2. A can steel sheet having at least the outer surface thereof provided with a Cr film having a film thickness of 0.01 to 1.0 μm as a lower layer and an Al—Sn alloy film having a film thickness of 0.05 to 5.0 μm as an upper layer. Characterized surface-treated steel sheet for cans.